1. Field of the Invention
The present invention relates to a block copolymer with rubber elasticity. More specifically, the instant invention is concerned with an ABA type block copolymer having an acrylic ester residue in its intermediate block, which may be used in applications wherein the (raw or starting materials used are required to possess rubber elasticity, for instance, as the (raw or starting) materials for elastomers, sealants, packings, adhesives, solvent type adhesive materials, hot-melt adhesive materials, heat sealants, vibration-proof materials, sound absorbers, solings, sports goods, toys, hoses, tubes, automotive parts and so on.
2. Prior Art
In many cases, block copolymers possess the properties inherent in their constitutional blocks.
Development of block copolymers having an acrylic ester residue in their intermediate blocks has thus been potentially expected because of an acrylic ester excelling in flexibility, weather resistance and chemical resistance. Until now in regard to block copolymers having an intermediate block of acrylic ester residues and their preparation, however, only the block copolymer synthesized with a polymeric peroxide has been proposed in, e.g., Japanese Patent Laid-Open Publication No. 61(1986)-287915.
However, the block copolymer proposed in that publication is a so-called AB type diblock copolymer. In general, the AB type diblock copolymer is free from elastic nature, say, rubber elasticity, since although one block is under constraint as a frozen or crystalline phase, yet the other is free. For that reason, such a diblock copolymer could not be used in various applications in which rubber elasticity is required, as already mentioned.